This invention is concerned with increasing the abrasion resistance of steel rails or steel rail wheels, or both.
As is well known, the service life of steel rails and rail wheels is predominantly determined by the wear thereof. Rail wheels are known to be used as a mono-bloc wheel (a single unitary wheel), or as an outer rim or wheel tire.
The steel rail and rail wheel coact during use such that each abrades the other, and there has been a long-felt need for means to reduce the abrasion of the two abrading partners which takes place between the wheel and the rail.
Many attempts have been made to reduce the abrasion between the rail and the rail wheel, and one such proposal is to increase the strength of the steels used. For this purpose, various alloying elements as well as variations in the heat treatments have been used to increase the strength of these two elements, see "Stahl und Eisen" 90 (1970, pages 922-928) and "Stahl und Eisen" 95 (1975, pages 1057-1062).
It is well known that abrasion is particularly troublesome in connection with curved rails. The publication "Eisenbahntechnische Rundschau" 22 (1973), on pages 214-218 sets forth details with respect to the special connection or relationship between the strength and abrasion behavior which takes place between curved rails and the rail wheel. For example, this publication sets forth that if the strength of the rail steel is increased by 200 N/mm, the abrasion will will drop to about one half of the original amount. With regard to the composition of material for use in rail wheels, reference is especially made to the publication "Glasers Annalen" 98 (1974), pages 93-100; this publication specifies that the abrasion characteristics of the rail wheels are improved with an increase in the strength of the material.
Heat treatment has also been used to decrease the amount of abrasion, and reference is made to "Glasers Annalen" 101 (1977), pages 103-109 which indicates that a change in the structure by heat treatment will have a favorable influence and effect and the reduction of the abrasion resistance between the rail and the rail wheels.
It has also been found that while certain alloying elements are suitable to reduce the abrasion resistance, the quantity of such alloying elements cannot be increased without other deleterious effects resulting. Specifically, it has been found that with the increase of certain of the alloying elements, certain undesired side effects result, and these also have to be taken into consideration. Specifically, there is an increased tendency to fracture due to brittleness and an increased tendency to crack due to hardening, and here reference is made to "Glasers Annalen" 88 (1964), pages 98-108 and 98 (1974), pages 93-100.
It is also known that the abrasion between the rail and the wheel can be reduced by the use of lubricants. These lubricants are applied to the contact surface between the wheel and the rail by means of lubricating devices which are used to lubricant the contact surfaces or by lubricating the wheel rim. Such lubrication can only be achieved in a restricted manner as the adhesion between the wheel and the rail must be maintained. Moreover, such lubrication must be constantly renewed, and the operating costs of the railway are increased. It is also well known that the heavy abrasion between the rail and the wheels can be reduced by welding an abrasion resistant working material onto the rails and wheels. However, as is also well known, problems can arise due to welding faults which in turn can lead to damages.
It is also known to alloy lead with steel to produce steels having improved machinability; see for example "Archiv fur das Eisenhuttenwesen" (1943), pages 65-76, and German Pat. No. 910,309. These publications teach that the addition of lead in the range of 0.03 percent to 0.48 percent provides for a considerable improvement in the cutting properties of cutting equipment. Furthermore, it is believed that the improved machinability is due to the finely distributed lead dispersions which facilitate the division and breaking up of the chips, and further that there is a reduction in the frictional resistance due to the lubricating effect between the working material to be machined and the cutting tool. Furthermore, since there is a reduction in the friction between the material during machining, the temperature is also reduced.
While this information has been available to experts and specialists skilled in the railroad art and in particular those working in the area of abrasion reduction for rails and rail wheels, the knowledge of adding lead to increase the machinability of steel has had no influence or bearing. There has apparently been no recognition or appreciation that the service life can be increased by adding lead to rail steels and wheel working materials, and that this increase in service life can go well beyond 50 percent and even beyond 100 percent for well known rail steels.
Conventional known natural hard steels for use in rails and rail wheels are known from UIC leaflet 860 V, 6th edition of 1, 1, 70 of from "Technische Lieferbedingungen der Deutschen Bundesbahn" TL 918 254, January 1972 edition. A survey in Table I of known natural hard steels is provided.
These natural hard steels can also be present in a heat treated state, e.g. after accelerated cooling from the rolling heat. Reference is also made to German Auslegeschrift No. 2,439,338 corresponding to U.S. Pat. No. 4,082,577 which disclose a special process for producing a very fine pearlitic structure which can be used in a rail steel.
Low-carbonized steels with a low minimum tensile strength is usually not suitable for rails or rail wheels.
It is therefore an object of the present invention to improve the abrasion resistance which takes place between the railroad rail and the rail wheel by simple measures.